How Much Evidence is Enough? Conventions of Causal Inference

One of the most important issues for science in the courtroom is the determination of causality. Like science in the courtroom, science in the regulatory arena can also bring a clash of cultures, misunderstanding, and controversy--especially when decisions must be made with some urgency with interested parties watching closely. Here, Kriebel discusses some conventions in the conduct of science and in the ways that scientific information is communicated to nonscientists that can make it difficult for judges, lawyers, regulators, and politicians to do their jobs making decisions about complex environmental and health issues

Lessons Learned: Solutions for Workplace Safety and Health

Provides case studies of workplace health hazards, regulatory actions taken, and solutions, including product and design alternatives; a synthesis of findings and lessons learned; and federal- and state-level recommendations

Causal models in epidemiology: past inheritance and genetic future

The eruption of genetic research presents a tremendous opportunity to epidemiologists to improve our ability to identify causes of ill health. Epidemiologists have enthusiastically embraced the new tools of genomics and proteomics to investigate gene-environment interactions. We argue that neither the full import nor limitations of such studies can be appreciated without clarifying underlying theoretical models of interaction, etiologic fraction, and the fundamental concept of causality. We therefore explore different models of causality in the epidemiology of disease arising out of genes, environments, and the interplay between environments and genes. We begin from Rothman's "pie" model of necessary and sufficient causes, and then discuss newer approaches, which provide additional insights into multifactorial causal processes. These include directed acyclic graphs and structural equation models. Caution is urged in the application of two essential and closely related concepts found in many studies: interaction (effect modification) and the etiologic or attributable fraction. We review these concepts and present four important limitations. 1. Interaction is a fundamental characteristic of any causal process involving a series of probabilistic steps, and not a second-order phenomenon identified after first accounting for "main effects". 2. Standard methods of assessing interaction do not adequately consider the life course, and the temporal dynamics through which an individual's sufficient cause is completed. Different individuals may be at different stages of development along the path to disease, but this is not usually measurable. Thus, for example, acquired susceptibility in children can be an important source of variation. 3. A distinction must be made between individual-based and population-level models. Most epidemiologic discussions of causality fail to make this distinction. 4. At the population level, there is additional uncertainty in quantifying interaction and assigning etiologic fractions to different necessary causes because of ignorance about the components of the sufficient cause

If Smoking Were Eliminated, Which US Counties Would Still Have High Rates of Smoking-Related Cancers?

Objective: to characterize the county variability of the impact of smoking elimination on rates of smoking-related cancers and explore whether common environmental indices predicted which metropolitan counties would experience high rates of smoking-related cancers even after smoking was eliminated. Methods: Surveillance, Epidemiology, and End Results Program (SEER) and Environmental Protection Agency (EPA) data were obtained. County level cancer rates for 257 metropolitan SEER counties, including the observed rates and those predicted after eliminating smoking, were derived via multilevel regression modeling and age standardized to the 2016 SEER population. Associations between the EPA’s Environmental Quality Index (EQI) scores and “Low Benefit” counties (counties that remain above the top 20th percentile of post-smoking elimination incidence rates) were explored via logistic regression. Results: Reductions in smoking-related cancer incidence ranged from 58.4 to 3.2%. The overall EQI (OR = 1.96, 95% CI [1.34, 2.86]) and the air quality index (OR = 5.99, 95% CI [3.20, 11.22]) scores predicted higher odds of being a “Low Benefit” county. Conclusions: Substantial inequities in the post-smoking elimination cancer rates were observed; air pollution appears to be a primary explanation for this. Cancer prevention in metropolitan counties with high levels of air pollution should prioritize pollution control at least as much as tobacco control

Invited Perspective: Eliminating Toxics to Prevent Disease: Asbestos Leads the Way

Countries that have consumed more asbestos have historically had higher mortality rates from asbestos-related diseases (ARDs) than countries with lower asbestos consumption. A research letter in this issue by Rath et al. provides a 15-y update on evidence for this link and uses this evidence to support calls for a worldwide ban on the use of asbestos. We find their results convincing, and we agree with the urgent need to stop producing and using asbestos. For those who might be skeptical of this conclusion or who are considering how much weight to give this evidence, we offer this perspective as occupational/environmental epidemiologists

Refrigerated transportation by motor common carriers : a management inquiry

"3/69/2.5M""The youthful trucking industry had fewer than 100 thousand vehicles 50 years ago. It registered 13.3 million trucks of all types in 1964. By capitalizing on speed and completeness and flexibility of service, this industry has become so important that it is an indispensable part of our modern food marketing system. As the shipping requirements of numerous commodities become more specific, the motor carrier industry is entering a new era of specialization to satisfy these demands and to increase profits. ... Little is known about the problems of refrigerated motor carriers and of the opportunities open for educational work by Extension marketing personnel. This study analyzes the use of refrigerated transportat10n by 15 Midwest motor common carriers and the carriers' problems that tend to interfere with business efficiency. The study method used is a firm-by-firm analysis of carriers."--First page.Wesley R. Kriebel (Extension Economist, Marketing and Transportation, Pennsylvania State University), David E. Moser (Extension Economist, Marketing and Transportation, University of Missouri--Columbia

Guidelines for an extension educational program in transportation

"This publication has been prepared primarily for Extension personnel assigned to develop a state-level educational program in transportation. It provides broad program guidelines as a reference or starting point for the transportation specialist. It will also be helpful to the Extension economist or marketing specialist who may be called upon to deal with transportation and physical handling problems encountered in a commodity marketing or firm management assignment."--First paragraphDavid E. Moser (Extension Economist, Marketing and Transportation ; University of Missouri), Wesley R. Kribel (Extension Economist, Marketing and Transportation ; Pennsylvania State University